1. Field of the Invention
The present invention is generally related to a photoresist material and, more particularly, to a photoresist material which can be effectively used as a reactive ion etch (RIE) barrier.
2. Description of the Prior Art
Photoresist materials are widely used in the semiconductor industry. A photoresist material can be easily patterned by imaging and developing, and the pattern created can then be transferred to an underlying substrate by etching. However, the known photoresist materials tend to erode themselves during etching, thereby limiting their utility as a stencil for patterning a substrate. Therefore, much effort has been made in using reactive ion etch (RIE) barriers in combination with photoresists and in chemically or physically altering a photoresist after patterning so that it will have the qualities of an RIE barrier. The RIE barriers are more resistant to etching and protect the underlying substrate in regions which are not to be patterned by etching.
FIG. 1 shows the process steps of a well known trilayer technique. First, a lift-off polymer 10 is applied to a wafer or substrate 12. A RIE barrier layer 14, such as hexamethyldisilazane (HMDS), silicon nitride (Si.sub.3 N.sub.4), or silicon dioxide (SiO.sub.2, often called quartz), is then applied over the lift-off polymer 10. Finally, a photoresist layer 16 is applied to the top to complete the trilayer structure. The lift-off polymer, RIE barrier layer, and photoresist layer can be applied by many well known techniques including using a plasma tool or by spinning procedures. The photoresist layer 16 is then patterned by imaging and developing. The pattern 18 is then transferred to the substrate 10 by first etching the RIE barrier layer 14 with CF.sub.4 and then etching the lift-off polymer 10 with O.sub.2 RIE. During O.sub.2 RIE, the photoresist 16 may erode away, however, the RIE barrier layer 14 remaining under the photoresist 16 will protect the underlying substrate 10. Metal 20 is then blanket deposited by evaporation or by other suitable techniques with the trilayer stacks serving as a stencil. Finally, the trilayer stacks are removed by dissolving the lift-off polymer 10 with an appropriate solvent. The trilayer process is expensive in that additional materials, process steps, and plasma tools are required.